Feasibility test and characterization of wheelchair everyday life log with smartphone-based electronic recording equipment

To comprehensively evaluate the usability and maneuverability of power wheelchairs (PWCs), it is important to systematically collect multimodal data related to wheelchair use from a real environment. In this study, we developed a wheelchair everyday life log system with smartphone-based electronic recording equipment (WELL-SphERE). The combination of a smartphone and a versatile A/D converter allows the measurement, transfer, and storage of various indicators, including the three-axis accelerations and angular velocities of a wheelchair body, GPS position, and joystick inputs. By employing a triaxial accelerometer mounted on the tip of a joystick, the system can directly quantify the joystick angular displacement without any modification of the existing driving system. We installed this system on two different types of PWCs and characterized the data logged during the test-driving. The comparison of the joystick inputs logged by the WELL-SphERE system with those electronically logged from the driving unit identified measurement errors caused by inertial movements of the wheelchair bodies. These errors, however, were ignorable if we consider the dead zone of the joystick displacements. A superimposed plot of the z-axis acceleration on a map demonstrates the effectiveness of WELL-SphERE in grasping the relationship between the terrain conditions and wheelchair behavior.